The field of the invention relates generally to electrical power systems including electronically controlled switches supplying power to a load, and more specifically to boost converter circuitry including a controlled impedance switch to connect a boosted voltage to a load.
Electrical power converter circuitry for DC circuits are generally known and in widespread use. Certain circuits are sometimes referred to as boost or buck converters and are used in a variety of applications, including but not limited to electrical power systems for vehicles. The boost converters typically receive input power at a first voltage Vin from a power supply such as a vehicle battery in one example, and output electrical power to a load at a second voltage Vout higher than the first voltage. Thus, by virtue of the boosted voltage, electrical loads may be driven from a power supply which would otherwise be insufficiently served by the power supply alone operating at the first voltage. In a vehicle environment, such loads may include, but are not necessarily limited to communications electronics, compressors, an anti-lock brake system (ABS) unit, and lighting systems.
In some known boost converter systems, a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) is provided and utilized as a controlled impedance switch between the boost converter and the load, so that the converted output voltage to a downstream load rises slowly, thus minimizing surge currents and the disruptions that abrupt voltage changes may otherwise cause. The more intelligent of these systems actively monitor current flow through the MOSFET, which allows the circuit to act as an Electronic Circuit Breaker (ECB), a Load Switch, and a Load Inrush Controller. The most intelligent of these systems recognize that for higher currents and voltages, the power dissipated in the MOSFET while in its linear region as it ramps up/down the output voltage could exceed the rated Safe Operating Area (SOA) of the MOSFET. To address such concerns, known systems have implemented active current and power limiting schemes, and Fault Timers to prevent the MOSFET from exceeding its SOA and potentially failing. While such techniques can be effective in some applications, they remain problematic for others, and improvements are desired.